The aims of this study were (1) to evaluate the short-term impact of convulsions on serum NfL (sNfL) levels in a cohort of children presenting with FS in comparison with children with febrile infections and epileptic seizures at an emergency department (ED); (2) to compare sNfL levels with other postictal serum biomarkers, namely, copeptin and prolactin; and (3) to characterize sNfL levels in the population of young children in general. The gene discussed is AVP; the disease is Feingold syndrome.